With and by: -(y)le / -(y)la

The ending -la/-le means with or by. It marks:

• a tool: kaşıkla (with a spoon), kalemle (with a pen)
• a means of transport: otobüsle (by bus), trenle (by train)
• a companion: arkadaşımla (with my friend)

It follows vowel harmony: -la after a, ı, o, u and -le after e, i, ö, ü. After a vowel add a buffer y: arabayla, gemiyle, suyla, annesiyle. The consonant before it does not soften: kaşıkla, uçakla.

The ending is the short form of the separate word ile, which never changes: otobüs ile, araba ile. Both are correct; in everyday speech the ending is more common. For pronouns (benimle, onlarla) see the Pronouns pack.